Advanced Search

nm

12238 Reputation

20 Badges

13 years, 255 days
Contact nm

MaplePrimes Activity


These are questions asked by nm

why limit fails when having two limits a...

nm 12238 Maple 2024
limit assertion
April 19 2024
1 2

Is it wrong to call limit like this

limit(expr,[y = y0,x=x0]);

vs

limit(expr,y = y0);
limit(%,x=x0);

The first one gives internal Maple error.  Worksheet attached. I would have expected both to work the same.

> 

interface(version);

`Standard Worksheet Interface, Maple 2024.0, Windows 10, March 01 2024 Build ID 1794891`

> 

Physics:-Version();

`The "Physics Updates" version in the MapleCloud is 1727 and is the same as the version installed in this computer, created 2024, April 17, 19:33 hours Pacific Time.`

> 

kernelopts('assertlevel'=2):
> 

expr:=3/2*(y-1)^(2/3)-3/2*x^2-c__1 = 0;
y0:=-7;
x0:=3;
limit(expr,[y = y0,x=x0]);
 

(3/2)*(y-1)^(2/3)-(3/2)*x^2-c__1 = 0

-7

3

Error, (in limit/multi/ldegree1) assertion failed

> 

expr:=3/2*(y-1)^(2/3)-3/2*x^2-c__1 = 0;
y0:=-7;
x0:=3;
limit(expr,y = y0);
limit(%,x=x0);

(3/2)*(y-1)^(2/3)-(3/2)*x^2-c__1 = 0

-7

3

-3+(3*I)*3^(1/2)-(3/2)*x^2-c__1 = 0

-33/2+(3*I)*3^(1/2)-c__1 = 0

 

 

Download limit_internal_error_maple_2024.mw

Error, (in anonymous procedure called fr...

nm 12238 Maple 2024
ode differential-equations odetest
April 19 2024
2 3

I still see these Maple internal errors in Maple 2024.

Now calling odetest.

The problem is that it is not possible to catch them.

Any suggestion what to do and what causes it?

11196

> 

interface(version);

`Standard Worksheet Interface, Maple 2024.0, Windows 10, March 01 2024 Build ID 1794891`

> 

Physics:-Version();

`The "Physics Updates" version in the MapleCloud is 1727 and is the same as the version installed in this computer, created 2024, April 17, 19:33 hours Pacific Time.`

> 

sol:=y(x) = (exp(RootOf(-sin(x)*tanh(1/2*_Z+1/2*c__1)^2+sin(x)+exp(_Z)))+sin(x))/sin(x);
ode:=diff(y(x),x)-cot(x)*(y(x)^(1/2)-y(x)) = 0;

y(x) = (exp(RootOf(-sin(x)*tanh((1/2)*_Z+(1/2)*c__1)^2+sin(x)+exp(_Z)))+sin(x))/sin(x)

diff(y(x), x)-cot(x)*(y(x)^(1/2)-y(x)) = 0

> 

try
   odetest(sol,ode,y(x));
catch:
   print("cought error ");
end try;

Error, (in anonymous procedure called from depends) too many levels of recursion

 

 

Download too_many_levels_of_recursion_calling_odetest_maple_2024.mw

odetest does not validate correct soluti...

nm 12238 Maple 2024
ode dsolve differential-equations
April 18 2024
1 0

I think I found another clitch in odetest.

dsolve gives correct solution to this first order ode with IC. But odetest does not verify that the solution is satisfied for the IC part, but only for the ode itself. 

Below worksheet confirms the solution is also valid for the IC.   So why odetest does not give 0 for the IC part?

``

> 

restart;

19644

> 

interface(version);

`Standard Worksheet Interface, Maple 2024.0, Windows 10, March 01 2024 Build ID 1794891`

> 

Physics:-Version();

`The "Physics Updates" version in the MapleCloud is 1727. The version installed in this computer is 1725 created 2024, April 15, 17:29 hours Pacific Time, found in the directory C:\Users\Owner\maple\toolbox\2024\Physics Updates\lib\`

> 

libname;

"C:\Users\Owner\maple\toolbox\2024\Physics Updates\lib", "C:\Program Files\Maple 2024\lib"

> 

ode:=x^2*diff(y(x),x)*cos(y(x))+1=0;
ic:=y(infinity)=Pi/3; #16/3*Pi;
sol:=dsolve([ode,ic]);
odetest(sol,[ode,ic])

x^2*(diff(y(x), x))*cos(y(x))+1 = 0

y(infinity) = (1/3)*Pi

y(x) = arcsin((1/2)*(3^(1/2)*x+2)/x)

[0, (1/3)*Pi]

> 

#we see that odetest think the solution does not verify the IC. But it does
> 

IC_eq:=Pi/3=limit(rhs(sol),x=infinity)

(1/3)*Pi = (1/3)*Pi

Download odetest_does_not_verfiy_correct_solution_maple_2024_april_18_2024.mw

I think what odetest did is not use limit when plugging in the values. That is why.

If we do not use limit, this is what happens:

IC_eq:=Pi/3=eval(rhs(sol),x=infinity)

And this explains the odetest output. It should have used limit.

ps. just in case also reported to Maplesoft support.

How to make ODESteps use the new nicer l...

nm 12238 Maple 2024
ode dsolve differential-equations
April 16 2024
1 0

I noticed that Student:-ODEs:-ODESteps does not use the newer subscripted constant of integrations for solution of odes which looks much nicer.

Is there a way to make it use same constant of integrations as dsolve() does? Compare  

This is on a worksheet using typesetting level extended. Worksheet is attached


 

> 

restart

18836

> 

interface(version);

`Standard Worksheet Interface, Maple 2024.0, Windows 10, March 01 2024 Build ID 1794891`

> 

Physics:-Version();

`The "Physics Updates" version in the MapleCloud is 1724 and is the same as the version installed in this computer, created 2024, April 15, 17:29 hours Pacific Time.`

> 

#to make Maple use the new constant of integrations. Is this still needed in Maple 2024?
dsolve(diff(y(x),x$9)=1,arbitraryconstants=subscripted):
pdsolve(diff(psi(x,t),x$9)=0,arbitraryfunctions=subscripted):
> 

ode := diff(y(x), x$2) + 2*y(x) = 0;
Student:-ODEs:-ODESteps(ode,y(x));

ode := diff(y(x), x, x)+2*y(x) = 0

"[[,,"Let's solve"],[,,((ⅆ)^2)/(ⅆx^2) y(x)+2 y(x)=0],["•",,"Highest derivative means the order of the ODE is" 2],[,,((ⅆ)^2)/(ⅆx^2) y(x)],["•",,"Characteristic polynomial of ODE"],[,,r^2+2=0],["•",,"Use quadratic formula to solve for" r],[,,r=(0+/-([]))/2],["•",,"Roots of the characteristic polynomial"],[,,r=(-ⅈ sqrt(2),ⅈ sqrt(2))],["•",,"1st solution of the ODE"],[,,y[1](x)=cos(sqrt(2) x)],["•",,"2nd solution of the ODE"],[,,y[2](x)=sin(sqrt(2) x)],["•",,"General solution of the ODE"],[,,y(x)=C1 y[1](x)+C2 y[2](x)],["•",,"Substitute in solutions"],[,,y(x)=C1 cos(sqrt(2) x)+C2 sin(sqrt(2) x)]]"

> 

#compare to this output
dsolve(ode,y(x));

y(x) = c__1*sin(2^(1/2)*x)+c__2*cos(2^(1/2)*x)


 

Download make_step_solution_use_new_constant_of_integration.mw

 

why mapleprimes removes tags from post?...

nm 12238 MaplePrimes
tags
April 14 2024
0 3

I noticed tags on the post  

https://mapleprimes.com/questions/238161-Why-Maple-Gives-Solution-To-Euler-Ode

keep disappearing. 

I added tags "differential equation" and "dsolve" and so on.  

Later on when I visit this site again I found the tags are all gone.

Why does Mapleprimes remove the tags on post?

Or is someone else removing the tags? If so, why? is something wrong with the tags I've added?

This happend twice on this one post. I noticed earlier today the tags were gone, so I added them again. And now I see the same thing. They are all gone.

First 50 51 52 53 54 55 56 Last Page 52 of 217